* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download No Slide Title
Phosphorylation wikipedia , lookup
G protein–coupled receptor wikipedia , lookup
Signal transduction wikipedia , lookup
P-type ATPase wikipedia , lookup
Protein (nutrient) wikipedia , lookup
Magnesium transporter wikipedia , lookup
Endomembrane system wikipedia , lookup
Protein structure prediction wikipedia , lookup
Intrinsically disordered proteins wikipedia , lookup
Cell nucleus wikipedia , lookup
Protein moonlighting wikipedia , lookup
Protein phosphorylation wikipedia , lookup
List of types of proteins wikipedia , lookup
Nuclear magnetic resonance spectroscopy of proteins wikipedia , lookup
Protein–protein interaction wikipedia , lookup
Proteolysis wikipedia , lookup
Western blot wikipedia , lookup
Protein mass spectrometry wikipedia , lookup
ESSENTIALS OF GLYCOBIOLOGY LECTURE 16 NUCLEAR, CYTOPLASMIC, AND MITOCHONDRIAL GLYCOSYLATION Hud Freeze Traditional Glycobiology Studies ER- and Golgi-based Glycosylation MAJOR FORMS OF CYTOPLASMIC GLYCOSYALTION Animals: Hyaluronan, Glycogen Plants: Cellulose Insects Yeast & Fungi: Chitin MITOCHONDRIAL GLYCOSYLATION FACT OR FICTION? SUGGESTIVE RESULTS FROM THE EARLY DAYS •Suggested by radio labeling with sugar precursors •Lectin binding studies SOME NAGGING PROBLEMS •Contamination by other cellular components, esp ER •How to get glycosyltransferases into mitochondria? •How do substrates enter? CLOSE FRIENDS ?? MITOCH ER QuickTime™ and a Video decompressor are needed to see this picture. ? GLYCOSYLATION IN MITOCHONDRIA? Metabolic labeling with 35S +/- deglycosylation 3H-Mannose labeling Specific mitochondrial protein complexes label with 3H-Man F1-ATPase (Complex-V) NADH-Ubiquinone-(Complex I) The glycoprotein binds to The lectin ConA Nuclear and Cytoplasmic Glycosylation In Favor Opposed • Many papers • Orientation of Transferases- Type II Membrane Proteins • Highly regarded journals • Many • Lectins Nuclear Localization Signals • Composition No site mapping • Metabolic Labeling •No structural analysis of glycan •Enzyme digestions •Purity CYTOSOLIC GLYCOSYLATION CYTOSOLIC GLYCOSYLATION Glycogenin is a Self Priming Glucosyl transferase 3 GN GN 2 Tyr-194 Tyr-194 GS UDP 1 UDP-Glc GN Tyr-194 GS Phosphorylase+ Debranching Enzyme UDP-Glc UDP 4 GS GS Tyr-194 GN Tyr-194 GN 5 Branching Enz+GS Intersubunit Priming Tyr-194 Tyr-194 Intrasubunit Priming Tyr-194 Tyr-194 CYTOSOLIC GLYCOSYLATION Stages of Dictyostelium Development Skp1 glycosylation pathway in Dictyostelium Most complex form of cytoplasmic glycosylation Verified Complex Cytoplasmic Glycosylation • Only demonstrated for a single protein, SkpI, in Dictyostelium • SkpI involved in ubiquitination of cell cycle proteins • Attached O-linked chain at Pro-143 (not conserved) which is first hydroxylated to HyPro • Gala-6GalaFuca1-2Galb1-3-GlcNAc-HyPro • GlcNAc and Fuc Transferase purified and shown to have very low Km for sugar nucleotides • First Gal and Fuc are added by single transferase • Mammalian homologs may not have this modification CYTOPLASMIC GLYCOSYLATION O-Mannose •UDP-Glc Transfers Glc1-P to Mannose on a cystosolic protein •62kD protein is Phosphoglucomutase (Glc-1-PGlc-6-P) •Transferase and phosphodiesterase found on many cells •Membrane association regulated by modification with Glc-1-P •Structure of underlying oligosaccharide not known CYTOPLASMIC GLYCOSYLATION CYTOSOLIC GLYCOSYLATION PROTEOGLYCANS MADE IN THE NUCLEUS NO DELIVERY TO NUCLEUS? MAYBE • GAG SUBFRACTION IS HIGHLY ENRICHED IN ISOLATED NUCLEI • SMALL FRACTION OF FGF FROM LYSOSOME MAY BE TRANSPORTED TO THE NUCLEUS MECHANISM? CYTOSOLIC GLYCOSYLATION Ubiquitination of a New Form of a-Synuclein by Parkin from Human Brain: Implications for Parkinson's Disease SCIENCE, July 13, 2001 aSp22 is an O-linked glycosylated isoform of a-synuclein. Failure of parkin to degrade it could cause some forms of PD Accumulation of an O-glycosylated form of a-synuclein In autosomal recessive forms of Parkinson’s disease? CYTOSOL E3-Ub-ligase co-incubation with O-glycosidase and sialidase A shifted the 22-kD species to a 16-kD position (31), where it now co-migrated with the unmodified S monomer, Sp16, from crude brain extracts (Fig. 5C). We conclude from our data obtained by mass spectrometry analysis (21) and these enzymatic digestions that Sp22 is a posttranslationally modified form of human Sp16 containing O-linked sugars. a3 b3 a-Thr/Ser 31. For enzymatic digestion of HP2A precipitates, N-glycosidase, sialidase A, endo-Oglycosidase and protein phosphatase-1 (Sigma) were used as per manufacturers' instructions. 21. The HP2A-specific 22-kD protein yielded tryptic peptides corresponding to aa 13-21, 44-58, 46-58, 59-80, 61-80, 81-96, and 81-97 of human Sp16 (GenBank accession # L08850), each ending with a lysine, as expected. DIGESTION OF O-LINKED GalNAc sugar chain-- 2 easy steps a3 1. a-Thr/Ser b3 SIALIDASE b3 a-Thr/Ser 2. b3 O-GLYCOSIDASE ARE THEY CORRECT OR NOT? WHAT’S YOUR OPINION? Summary •O-GlcNAc is only one form of cytoplasmic glycosylation • Hyaluronan, glycogen, cellulose and chitin are examples • Other forms of Cytoplasmic glycosylation exist Transferases and genes are characterized • The roles of specific sugar chains in not known in most cases • Lack of structural information is often a key deficiency • Mitochondria may acquire N-glycosylated proteins from ER • Other forms may exist, but proof requires structural analysis